implementation bael-6949 (#15643)
* implementation * feedbacks --------- Co-authored-by: technoddy <mail.technoddy@gmail.com>
This commit is contained in:
Sam
GitHub
parent
08d29f73b3
commit
f254e8f751
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@ -6,6 +6,18 @@
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<artifactId>core-java-persistence-3</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<name>core-java-persistence-3</name>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>17</source>
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<target>17</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<packaging>jar</packaging>
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<parent>
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package jdbcpagination;
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import java.sql.Connection;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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public class PaginationLogic {
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public static ResultSet readPageWithLimitAndOffset(Connection connection, int offset, int pageSize) throws SQLException {
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String sql = """
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SELECT * FROM employees
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LIMIT ? OFFSET ?
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""";
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PreparedStatement preparedStatement = connection.prepareStatement(sql);
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preparedStatement.setInt(1, pageSize);
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preparedStatement.setInt(2, offset);
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return preparedStatement.executeQuery();
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}
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public static ResultSet readPageWithSortedKeys(Connection connection, int lastFetchedId, int pageSize) throws SQLException {
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String sql = """
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SELECT * FROM employees
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WHERE id > ? LIMIT ?
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""";
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PreparedStatement preparedStatement = connection.prepareStatement(sql);
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preparedStatement.setInt(1, lastFetchedId);
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preparedStatement.setInt(2, pageSize);
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return preparedStatement.executeQuery();
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}
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}
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package jdbcpagination;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.stream.IntStream;
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import org.junit.jupiter.api.AfterAll;
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import org.junit.jupiter.api.BeforeAll;
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import org.junit.jupiter.api.Test;
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public class PaginationLogicUnitTest {
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private static Connection connection = null;
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private static final String JDBC_URL = "jdbc:h2:mem:testDB";
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private static final String USERNAME = "dbUser";
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private static final String PASSWORD = "dbPassword";
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@BeforeAll
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public static void setup() throws Exception {
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connection = connect(JDBC_URL, USERNAME, PASSWORD);
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populateDB();
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}
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@AfterAll
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public static void tearDown() throws SQLException {
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destroyDB();
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}
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@Test
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public void givenDBPopulated_WhenReadPaginatedWithLimitAndOffset_ThenReturnsPaginatedResult() throws SQLException {
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int offset = 0; // offset is set to 0 and keep updating with pageSize
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int pageSize = 100_000;
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int totalPages = 0;
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while (true) {
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ResultSet resultSet = PaginationLogic.readPageWithLimitAndOffset(connection, offset, pageSize);
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if (!resultSet.next())
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break;
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List<String> resultPage = new ArrayList<>();
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do {
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resultPage.add(resultSet.getString("first_name"));
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} while (resultSet.next());
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assertEquals("firstname" + (resultPage.size() * (totalPages + 1)), resultPage.get(resultPage.size() - 1));
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offset += pageSize;
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totalPages++;
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}
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assertEquals(10, totalPages);
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}
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@Test
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public void givenDBPopulated_WhenReadPaginatedWithSortedKeys_ThenReturnsPaginatedResult() throws SQLException {
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// find min and max ID
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PreparedStatement preparedStatement = connection.prepareStatement("SELECT min(id) as min_id, max(id) as max_id FROM employees");
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ResultSet resultSet = preparedStatement.executeQuery();
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resultSet.next();
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int minId = resultSet.getInt("min_id");
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int maxId = resultSet.getInt("max_id");
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int lastFetchedId = 0; // assign lastFetchedId to minId
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int pageSize = 100_000;
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int totalPages = 0;
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while ((lastFetchedId + pageSize) <= maxId) {
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resultSet = PaginationLogic.readPageWithSortedKeys(connection, lastFetchedId, pageSize);
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if (!resultSet.next())
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break;
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List<String> resultPage = new ArrayList<>();
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do {
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resultPage.add(resultSet.getString("first_name"));
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lastFetchedId = resultSet.getInt("id");
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} while (resultSet.next());
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assertEquals("firstname" + (resultPage.size() * (totalPages + 1)), resultPage.get(resultPage.size() - 1));
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totalPages++;
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}
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assertEquals(10, totalPages);
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}
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private static void destroyDB() throws SQLException {
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String destroy = """
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DROP table IF EXISTS EMPLOYEES;
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""";
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connection.prepareStatement(destroy)
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.execute();
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}
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private static void populateDB() throws SQLException {
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String createTable = """
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CREATE TABLE EMPLOYEES (
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id SERIAL PRIMARY KEY,
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first_name VARCHAR(50),
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last_name VARCHAR(50),
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salary DECIMAL(10, 2)
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);
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""";
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PreparedStatement preparedStatement = connection.prepareStatement(createTable);
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preparedStatement.execute();
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String load = """
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INSERT INTO EMPLOYEES (first_name, last_name, salary)
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VALUES(?,?,?)
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""";
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IntStream.rangeClosed(1, 1_000_000)
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.forEach(i -> {
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PreparedStatement preparedStatement1 = null;
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try {
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preparedStatement1 = connection.prepareStatement(load);
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preparedStatement1.setString(1, "firstname" + i);
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preparedStatement1.setString(2, "lastname" + i);
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preparedStatement1.setDouble(3, 100_000 + (1_000_000 - 100_000) + Math.random());
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preparedStatement1.execute();
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} catch (SQLException e) {
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throw new RuntimeException(e);
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}
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});
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}
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public static Connection connect(String url, String user, String password) throws SQLException {
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Connection connection = DriverManager.getConnection(url, user, password);
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if (connection != null) {
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System.out.println("Connected to database");
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}
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return connection;
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}
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}
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